HTML::Template::SYNTAXUser Contributed Perl DocumentaHTML::Template::SYNTAX(3)NAMEHTML::Template::SYNTAX - syntax of html template language for
HTML::Template
SYNOPSIS
This help is only on syntax of html template files. For perl interface
of HTML::Template::Pro you should see "SYNOPSIS" in
HTML::Template::PerlInterface.
First you make a template - this is just a normal HTML file with a few
extra tags, the simplest being <TMPL_VAR>
For example, test.tmpl:
<html>
<head><title>Test Template</title>
<body>
My Home Directory is <TMPL_VAR NAME=HOME>
<p>
My Path is set to <TMPL_VAR NAME=PATH>
</body>
</html>
Now define the value for HOME and PATH, for example, in perl it will
look like
$template->param(HOME => $ENV{HOME});
$template->param(PATH => $ENV{PATH});
and process the template. If all is well in the universe this should
show something like this in your browser:
My Home Directory is /home/some/directory
My Path is set to /bin;/usr/bin
DESCRIPTION
This module attempts to make using HTML templates simple and natural.
It extends standard HTML with a few new HTML-esque tags - <TMPL_VAR>,
<TMPL_LOOP>, <TMPL_INCLUDE>, <TMPL_IF>, <TMPL_ELSE> and <TMPL_UNLESS>.
(HTML::Template::Pro also supports <TMPL_ELSIF> tag.) The file written
with HTML and these new tags is called a template. It is usually saved
separate from your script - possibly even created by someone else!
Using this module you fill in the values for the variables, loops and
branches declared in the template. This allows you to separate design
- the HTML - from the data, which you generate in the Perl script.
This module is licensed under the (L)GPL or perl license. See the
LICENSE section below for more details.
TUTORIAL
If you're new to HTML::Template, I suggest you start with the
introductory article available on the HTML::Template website:
http://html-template.sourceforge.net
MOTIVATION
It is true that there are a number of packages out there to do HTML
templates. On the one hand you have things like HTML::Embperl which
allows you freely mix Perl with HTML. On the other hand lie home-grown
variable substitution solutions. Hopefully the module can find a place
between the two.
One advantage of this module over a full HTML::Embperl-esque solution
is that it enforces an important divide - design and programming. By
limiting the programmer to just using simple variables and loops in the
HTML, the template remains accessible to designers and other non-perl
people. The use of HTML-esque syntax goes further to make the format
understandable to others. In the future this similarity could be used
to extend existing HTML editors/analyzers to support HTML::Template.
An advantage of this module over home-grown tag-replacement schemes is
the support for loops. In my work I am often called on to produce
tables of data in html. Producing them using simplistic HTML templates
results in CGIs containing lots of HTML since the HTML itself cannot
represent loops. The introduction of loop statements in the HTML
simplifies this situation considerably. The designer can layout a
single row and the programmer can fill it in as many times as necessary
- all they must agree on is the parameter names.
For all that, I think the best thing about this module is that it does
just one thing and it does it quickly and carefully. It doesn't try to
replace Perl and HTML, it just augments them to interact a little
better. And it's pretty fast.
THE TAGS
GENERAL TAG SYNTAX
A generic HTML::Template tag that is supported by HTML::Template::Pro
looks like <TMPL_SOMETHING A="B" [C="D" ...]>. Tags are case-
insensitve: <tmpl_something a="B" [c="D" ...]> is acceptable. Single
quotes can be used, <TMPL_SOMETHING A='B' [C='D' ...]> quotes can be
omitted, <TMPL_SOMETHING A=B ... > and option name could be often
guessed as in <TMPL_SOMETHING B>.
template tags could be decorated as html comments <!-- TMPL_SOMETHING
A="B" -->
Also, as HTML::Template::Pro extension (starting from version 0.90),
template tags could also be decorated as xml <TMPL_SOMETHING A="B" />
See NOTES.
TMPL_VAR
<TMPL_VAR NAME="PARAMETER_NAME">
The <TMPL_VAR> tag is very simple. For each <TMPL_VAR> tag in the
template you call $template->param(PARAMETER_NAME => "VALUE"). When
the template is output the <TMPL_VAR> is replaced with the VALUE text
you specified. If you don't set a parameter it just gets skipped in
the output.
Optionally you can use the "ESCAPE=HTML" option in the tag to indicate
that you want the value to be HTML-escaped before being returned from
output (the old ESCAPE=1 syntax is still supported). This means that
the ", <, >, and & characters get translated into ", <, >
and & respectively. This is useful when you want to use a TMPL_VAR
in a context where those characters would cause trouble. Example:
<input name=param type=text value="<TMPL_VAR NAME="PARAM">">
If you called "param()" with a value like sam"my you'll get in trouble
with HTML's idea of a double-quote. On the other hand, if you use
ESCAPE=HTML, like this:
<input name=param type=text value="<TMPL_VAR ESCAPE=HTML NAME="PARAM">">
You'll get what you wanted no matter what value happens to be passed in
for param. You can also write ESCAPE="HTML", ESCAPE='HTML' and
ESCAPE='1'.
"ESCAPE=0" and "ESCAPE=NONE" turn off escaping, which is the default
behavior.
There is also the "ESCAPE=URL" option which may be used for VARs that
populate a URL. It will do URL escaping, like replacing ' ' with '+'
and '/' with '%2F'.
There is also the "ESCAPE=JS" option which may be used for VARs that
need to be placed within a Javascript string. All \n, \r, ' and "
characters are escaped.
You can assign a default value to a variable with the DEFAULT
attribute. For example, this will output "the devil gave me a taco" if
the "who" variable is not set.
The <TMPL_VAR NAME=WHO DEFAULT=devil> gave me a taco.
TMPL_LOOP
<TMPL_LOOP NAME="LOOP_NAME"> ... </TMPL_LOOP>
The <TMPL_LOOP> tag is a bit more complicated than <TMPL_VAR>. The
<TMPL_LOOP> tag allows you to delimit a section of text and give it a
name. Inside this named loop you place <TMPL_VAR>s. Now you pass to
"param()" a list (an array ref) of parameter assignments (hash refs)
for this loop. The loop iterates over the list and produces output
from the text block for each pass. Unset parameters are skipped.
Here's an example:
In the template:
<TMPL_LOOP NAME=EMPLOYEE_INFO>
Name: <TMPL_VAR NAME=NAME> <br>
Job: <TMPL_VAR NAME=JOB> <p>
</TMPL_LOOP>
In the script:
$template->param(EMPLOYEE_INFO => [
{ name => 'Sam', job => 'programmer' },
{ name => 'Steve', job => 'soda jerk' },
]
);
print $template->output();
The output in a browser:
Name: Sam
Job: programmer
Name: Steve
Job: soda jerk
As you can see above the <TMPL_LOOP> takes a list of variable
assignments and then iterates over the loop body producing output.
Often you'll want to generate a <TMPL_LOOP>'s contents
programmatically. Here's an example of how this can be done (many
other ways are possible!):
# a couple of arrays of data to put in a loop:
my @words = qw(I Am Cool);
my @numbers = qw(1 2 3);
my @loop_data = (); # initialize an array to hold your loop
while (@words and @numbers) {
my %row_data; # get a fresh hash for the row data
# fill in this row
$row_data{WORD} = shift @words;
$row_data{NUMBER} = shift @numbers;
# the crucial step - push a reference to this row into the loop!
push(@loop_data, \%row_data);
}
# finally, assign the loop data to the loop param, again with a
# reference:
$template->param(THIS_LOOP => \@loop_data);
The above example would work with a template like:
<TMPL_LOOP NAME="THIS_LOOP">
Word: <TMPL_VAR NAME="WORD"> <br>
Number: <TMPL_VAR NAME="NUMBER"> <p>
</TMPL_LOOP>
It would produce output like:
Word: I
Number: 1
Word: Am
Number: 2
Word: Cool
Number: 3
<TMPL_LOOP>s within <TMPL_LOOP>s are fine and work as you would expect.
If the syntax for the "param()" call has you stumped, here's an example
of a param call with one nested loop:
$template->param(LOOP => [
{ name => 'Bobby',
nicknames => [
{ name => 'the big bad wolf' },
{ name => 'He-Man' },
],
},
],
);
Basically, each <TMPL_LOOP> gets an array reference. Inside the array
are any number of hash references. These hashes contain the
name=>value pairs for a single pass over the loop template.
Inside a <TMPL_LOOP>, the only variables that are usable are the ones
from the <TMPL_LOOP>. The variables in the outer blocks are not
visible within a template loop. For the computer-science geeks among
you, a <TMPL_LOOP> introduces a new scope much like a perl subroutine
call. If you want your variables to be global you can use
'global_vars' option to new() described below.
TMPL_INCLUDE
<TMPL_INCLUDE NAME="filename.tmpl">
<TMPL_INCLUDE EXPR="function_call, variable, expression" DEFAULT='some_file'>
This tag includes a template directly into the current template at the
point where the tag is found. The included template contents are used
exactly as if its contents were physically included in the master
template.
The file specified can be an absolute path (beginning with a '/' under
Unix, for example). If it isn't absolute, the path to the enclosing
file is tried first. After that the path in the environment variable
HTML_TEMPLATE_ROOT is tried, if it exists. Next, the "path" option is
consulted, first as-is and then with HTML_TEMPLATE_ROOT prepended if
available. As a final attempt, the filename is passed to open()
directly. See below for more information on HTML_TEMPLATE_ROOT and the
"path" option to new().
As a protection against infinitly recursive includes, an arbitrary
limit of 10 levels deep is imposed. You can alter this limit with the
"max_includes" option. See the entry for the "max_includes" option
below for more details.
For the <TMPL_INCLUDE EXPR=".."> see "INCLUDE extension to Expr" for
more details.
TMPL_IF
<TMPL_IF NAME="PARAMETER_NAME"> ... </TMPL_IF>
The <TMPL_IF> tag allows you to include or not include a block of the
template based on the value of a given parameter name. If the
parameter is given a value that is true for Perl - like '1' - then the
block is included in the output. If it is not defined, or given a
false value - like '0' - then it is skipped. The parameters are
specified the same way as with TMPL_VAR.
Example Template:
<TMPL_IF NAME="BOOL">
Some text that only gets displayed if BOOL is true!
</TMPL_IF>
Now if you call $template->param(BOOL => 1) then the above block will
be included by output.
<TMPL_IF> </TMPL_IF> blocks can include any valid HTML::Template
construct - VARs and LOOPs and other IF/ELSE blocks. Note, however,
that intersecting a <TMPL_IF> and a <TMPL_LOOP> is invalid.
Not going to work:
<TMPL_IF BOOL>
<TMPL_LOOP SOME_LOOP>
</TMPL_IF>
</TMPL_LOOP>
If the name of a TMPL_LOOP is used in a TMPL_IF, the IF block will
output if the loop has at least one row. Example:
<TMPL_IF LOOP_ONE>
This will output if the loop is not empty.
</TMPL_IF>
<TMPL_LOOP LOOP_ONE>
....
</TMPL_LOOP>
WARNING: Much of the benefit of HTML::Template is in decoupling your
Perl and HTML. If you introduce numerous cases where you have TMPL_IFs
and matching Perl if()s, you will create a maintenance problem in
keeping the two synchronized. I suggest you adopt the practice of only
using TMPL_IF if you can do so without requiring a matching if() in
your Perl code.
TMPL_ELSIF
<TMPL_IF NAME="PARAMETER_NAME1"> ...
<TMPL_ELSIF NAME="PARAMETER_NAME2"> ...
<TMPL_ELSIF NAME="PARAMETER_NAME3"> ...
<TMPL_ELSE> ... </TMPL_IF>
WARNING: TMPL_ELSIF is a HTML::Template::Pro extension! It is not
supported in HTML::Template (as of 2.9).
TMPL_ELSE
<TMPL_IF NAME="PARAMETER_NAME"> ... <TMPL_ELSE> ... </TMPL_IF>
You can include an alternate block in your TMPL_IF block by using
TMPL_ELSE. NOTE: You still end the block with </TMPL_IF>, not
</TMPL_ELSE>!
Example:
<TMPL_IF BOOL>
Some text that is included only if BOOL is true
<TMPL_ELSE>
Some text that is included only if BOOL is false
</TMPL_IF>
TMPL_UNLESS
<TMPL_UNLESS NAME="PARAMETER_NAME"> ... </TMPL_UNLESS>
This tag is the opposite of <TMPL_IF>. The block is output if the
CONTROL_PARAMETER is set false or not defined. You can use <TMPL_ELSE>
with <TMPL_UNLESS> just as you can with <TMPL_IF>.
Example:
<TMPL_UNLESS BOOL>
Some text that is output only if BOOL is FALSE.
<TMPL_ELSE>
Some text that is output only if BOOL is TRUE.
</TMPL_UNLESS>
If the name of a TMPL_LOOP is used in a TMPL_UNLESS, the UNLESS block
output if the loop has zero rows.
<TMPL_UNLESS LOOP_ONE>
This will output if the loop is empty.
</TMPL_UNLESS>
<TMPL_LOOP LOOP_ONE>
....
</TMPL_LOOP>
NOTES
HTML::Template's tags are meant to mimic normal HTML tags. However,
they are allowed to "break the rules". Something like:
<img src="<TMPL_VAR IMAGE_SRC>">
is not really valid HTML, but it is a perfectly valid use and will work
as planned.
The "NAME=" in the tag is optional, although for extensibility's sake I
recommend using it. Example - "<TMPL_LOOP LOOP_NAME>" is acceptable.
If you're a fanatic about valid HTML and would like your templates to
conform to valid HTML syntax, you may optionally type template tags in
the form of HTML comments. This may be of use to HTML authors who would
like to validate their templates' HTML syntax prior to HTML::Template
processing, or who use DTD-savvy editing tools.
<!-- TMPL_VAR NAME=PARAM1 -->
In order to realize a dramatic savings in bandwidth, the standard (non-
comment) tags will be used throughout this documentation.
EXPR EXTENSION
This module supports an extension to HTML::Template which allows
expressions in the template syntax which was implemented in
HTML::Template::Expr. See HTML::Template::Expr for details.
Expression support includes comparisons, math operations, string
operations and a mechanism to allow you add your own functions at
runtime. The basic syntax is:
<TMPL_IF EXPR="banana_count > 10">
I've got a lot of bananas.
</TMPL_IF>
This will output "I've got a lot of bananas" if you call:
$template->param(banana_count => 100);
In your script. <TMPL_VAR>s also work with expressions:
I'd like to have <TMPL_VAR EXPR="banana_count * 2"> bananas.
This will output "I'd like to have 200 bananas." with the same param()
call as above.
BASIC SYNTAX
Variables
Variables are unquoted alphanumeric strings with the same restrictions
as variable names in HTML::Template. Their values are set through
param(), just like normal HTML::Template variables. For example, these
two lines are equivalent:
<TMPL_VAR EXPR="foo">
<TMPL_VAR NAME="foo">
Emiliano Bruni extension to Expr
original HTML::Template allows almost arbitrary chars in parameter
names, but original HTML::Template::Expr (as to 0.04) allows variables
in the 'EXPR' tag to be only m![A-Za-z_][A-Za-z0-9_]*!.
With this extension, arbitrary chars can be used in variable name
inside the 'EXPR' tag if bracketed in ${}, as, for example,
EXPR="${foo.bar} eq 'a'". Note that old bracketing into {} is
considered obsolete, as it will clash with JSON assignments like A = {
"key" => "val" }.
COMPATIBILITY WARNING. Currently, this extension is not present in
HTML::Template::Expr (as of 0.04).
INCLUDE extension to Expr
With this extension, you can write something like <TMPL_INCLUDE
EXPR="variable">
or <TMPL_INCLUDE EXPR="function_call()">, or even <TMPL_INCLUDE
EXPR="function_call(VAR1,VAR2,func2()) DEFAULT='some_file'">
SECURITY WARNING. Using of this extension with untrasted values of
variables is a potential security leak (as in <TMPL_INCLUDE
EXPR="USER_INPUT"> with USER_INPUT='/etc/passwd'). Omit it unless you
know what you are doing.
COMPATIBILITY WARNING. Currently, this extension is not present in
HTML::Template::Expr (as of 0.04).
Constants
Numbers are unquoted strings of numbers and may have a single "." to
indicate a floating point number. For example:
<TMPL_VAR EXPR="10 + 20.5">
String constants must be enclosed in quotes, single or double. For
example:
<TMPL_VAR EXPR="sprintf('%d', foo)">
Note that the original parser of HTML::Template::Expr is currently
(0.04) rather simple, so if you need backward compatibility all
compound expressions must be parenthesized.
Backward compatible examples:
<TMPL_VAR EXPR="(10 + foo) / bar">
<TMPL_IF EXPR="(foo % 10) > (bar + 1)">
Nevertheless, in HTML::Template::Pro, you can safely write things like
<TMPL_VAR EXPR="1+2*foo/bar^2 ">
with proper priority of operations.
Pattern in a regular expression must be enclosed with "/":
<TMPL_VAR EXPR="foo =~ /bar/">
COMPARISON
Here's a list of supported comparison operators:
· Numeric Comparisons
· <
· >
· ==
· !=
· >=
· <=
· <=>
· String Comparisons
· gt
· lt
· eq
· ne
· ge
· le
· cmp
MATHEMATICS
The basic operators are supported:
· +
· -
· *
· /
· %
· ^ (not supported in HTML::Template::Expr)
There are also some mathy functions. See the FUNCTIONS section below.
LOGIC
Boolean logic is available:
· && (synonym: and)
· || (synonym: or)
REGULAR EXPRESSION SUPPORT
regexp support is added to HTML::Template::Expr and HTML::Template::Pro
by Stanislav Yadykin <tosick at altlinux.ru>. Currently it is not
included in official distribution of HTML::Template::Expr.
Standard regexp syntax:
· =~
· !~
FUNCTIONS
The following functions are available to be used in expressions. See
perldoc perlfunc for details.
· sprintf
· substr (2 and 3 arg versions only)
· lc
· lcfirst
· uc
· ucfirst
· length
· defined
· abs
· atan2
· cos
· exp
· hex
· int
· log
· oct
· rand
· sin
· sqrt
· srand
All functions must be called using full parenthesis. For example, this
is a syntax error:
<TMPL_IF expr="defined foo">
But this is good:
<TMPL_IF expr="defined(foo)">
EXPR: DEFINING NEW FUNCTIONS
You may also define functions of your own. See
HTML::Template::PerlInterface for details.
AUTHOR
Sam Tregar, sam@tregar.com (Main text)
I. Vlasenko, <viy@altlinux.org> (Pecularities of HTML::Template::Pro)
LICENSE
HTML::Template : A module for using HTML Templates with Perl
Copyright (C) 2000-2008 Sam Tregar (sam@tregar.com)
This module is free software; you can redistribute it and/or modify it
under the terms of either:
a) the GNU General Public License as published by the Free Software
Foundation; either version 2, or (at your option) any later version,
or
b) the "Artistic License" which comes with this module.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either
the GNU General Public License or the Artistic License for more details.
You should have received a copy of the Artistic License with this
module, in the file ARTISTIC. If not, I'll be glad to provide one.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA
perl v5.14.2 2010-09-06 HTML::Template::SYNTAX(3)
